Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$234.85	9.145%	$256.327	$256.33	$256.35	$256.30
Purchase #2	$81.71	4.336%	$85.2529	$85.25	$85.25	$85.30
Purchase #3	$148.98	7.324%	$159.8913	$159.89	$159.90	$159.90
Purchase #4	$249.72	9.227%	$272.7617	$272.76	$272.75	$272.80
Purchase #5	$103.85	3.502%	$107.4868	$107.49	$107.50	$107.50
Purchase #6	$196.29	6.649%	$209.3413	$209.34	$209.35	$209.30
Purchase #7	$91.39	3.477%	$94.5676	$94.57	$94.55	$94.60
7 purchase totals =	$1,106.79		$1,185.6286	$1,185.63	$1,185.65	$1,185.70